Occupancy at Odds with Building Energy Use

05/22/2012 |

Your HVAC system could be heating or cooling empty areas. To address this energy waste, consider implementing dynamic controls or repurposing spaces.

Energy use does not always correspond to occupancy, according to MIT researchers.

A recent study finds that while electricity use typically corresponds to occupancy in observed spaces, the building’s HVAC loads do not. This represents wasted energy consumption and an opportunity to create savings through controls and adjustments.

The paper, “ENERNET: Studying the Dynamic Relationship between Building Occupancy and Energy Consumption,” examines two different types of MIT buildings.

Building 37 houses a combination of offices, classrooms, and labs, whereas Building E52 has a sizable entrance atrium and a large number of offices. The researchers used the number of WiFi connections as a proxy for occupancy.

When a building suddenly shifts occupancy, such as during lunch or at the end of the day, HVAC systems can continue to run at higher levels than necessary, wasting energy in empty spaces. More dynamic energy use can create huge savings with technologies like sensor-based thermostats that control temperatures.

In addition to controls, existing spaces can also be repurposed. For example, a once rarely used common space at MIT now hosts a snack bar, allowing its occupancy to more closely match the space’s energy use.

The researchers suggest that space use within buildings can be planned to conserve energy, citing the example of high-occupancy offices positioned around a lecture hall to keep the hall warmer.


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